I couldn't agree more. I pushed to get the place I worked for to use Slack when it first launched, moving us off AIM (ha!). Our use of Slack when we shared an office in the twenty-teens was so much better than the use I've seen of Slack/competitors on fully-remote teams.
I wonder if it's because the failure mode was, as you said, to "drop by." Now the failure mode is... just failure.